Ablation catheter and method for isolating a pulmonary vein

ABSTRACT

A catheter assembly and method for treatment of cardiac arrhythmia, for example, atrial fibrillation, by electrically isolating a vessel, such as a pulmonary vein, from a chamber, such as the left atrium. The catheter assembly includes a catheter body and at least one electrode. The catheter body includes a proximal portion, an intermediate portion and a distal portion. The intermediate portion extends from the proximal portion and defines a longitudinal axis. The distal portion extends from the intermediate portion and forms a substantially closed loop transverse to the longitudinal axis. The at least one electrode is disposed along the loop. With this configuration, the loop is axially directed into contact with the chamber wall about the vessel ostium. Upon energization, the electrode ablates a continuous lesion pattern about the vessel ostium, thereby electrically isolating the vessel from the chamber.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an ablation catheter fortreatment of cardiac arrhythmia, for example atrial fibrillation. Moreparticularly, it relates to an ablation catheter configured toelectrically isolate a vessel, such as a pulmonary vein, from a chamber,such as the left atrium with a continuous lesion pattern and a methodfor forming such a lesion pattern.

[0002] The heart includes a number of pathways that are responsible forthe propagation of signals necessary to produce continuous, synchronizedcontractions. Each contraction cycle begins in the right atrium where asinoatral node initiates an electrical impulse. This impulse thenspreads across the right atrium to the left atrium, stimulating theatria to contract. The chain reaction continues from the atria to theventricles by passing through a pathway known as the atrioventricular(AV) node or junction, which acts as an electrical gateway to theventricles. The AV junction delivers the signal to the ventricles whilealso slowing it, so the atria can relax before the ventricles contract.

[0003] Disturbances in the heart's electrical system may lead to variousrhythmic problems that can cause the heart to beat irregularly, too fastor too slow. Irregular heart beats, or arrhythmia, are caused byphysiological or pathological disturbances in the discharge ofelectrical impulses from the sinoatrial node, in the transmission of thesignal through the heart tissue, or spontaneous, unexpected electricalsignals generated within the heart. One type of arrhythmia istachycardia, which is an abnormal rapidity of heart action. There areseveral different forms of atrial tachycardia, including atrialfibrillation and atrial flutter. With atrial fibrillation, instead of asingle beat, numerous electrical impulses are generated by depolarizingtissue at one or more locations in the atria (or possibly otherlocations). These unexpected electrical impulses produce irregular,often rapid heartbeats in the atrial muscles and ventricles. Patientsexperiencing atrial fibrillation may suffer from fatigue, activityintolerance, dizziness and even strokes.

[0004] The precise cause of atrial fibrillation, and in particular thedepolarizing tissue causing “extra” electrical signals, is currentlyunknown. As to the location of the depolarizing tissue, it is generallyagreed that the undesired electrical impulses often originate in theleft atrial region of the heart. Recent studies have expanded upon thisgeneral understanding, suggesting that nearly 90% of these “focaltriggers” or electrical impulses are generated in one (or more) of thefour pulmonary veins (PV) extending from the left atrium. In thisregard, as the heart develops from an embryotic stage, left atriumtissue may grow or extend a short distance into one or more of the PVs.It has been postulated that this tissue may spontaneously depolarize,resulting in an unexpected electrical impulse(s) propagating into theleft atrium and along the various electrical pathways of the heart.

[0005] A variety of different atrial fibrillation treatment techniquesare available, including drugs, surgery, implants, and catheterablation. While drugs may be the treatment of choice for some patients,drugs typically only mask the symptoms and do not cure the underlyingcause. Implantable devices, on the other hand, usually correct anarrhythmia only after it occurs. Surgical and catheter-based treatments,in contrast, will actually cure the problem by ablating the abnormaltissue or accessory pathway responsible for the atrial fibrillation. Thecatheter-based treatments rely on the application of various destructiveenergy sources to the target tissue, including direct current electricalenergy, radiofrequency electrical energy, laser energy, and the like.The energy source, such as an ablating electrode, is normally disposedalong a distal portion of a catheter.

[0006] Most ablation catheter techniques employed to treat atrialfibrillation focus upon locating the ablating electrode, or a series ofablating electrodes, along extended target sections of the left atriumwall. Because the atrium wall, and thus the targeted site(s), isrelatively tortuous, the resulting catheter design includes multiplecurves, bends, extensions, etc. In response to recent studies indicatingthat the unexpected electrical impulses are generated within a PV,efforts have been made to ablate tissue within the PV itself. Obviously,the prior catheter designs incorporating convoluted, multiple bends arenot conducive to placement within a PV. Instead, a conventional“straight ended” ablation catheter has been employed. While thistechnique of tissue ablation directly within a PV has been performedwith relatively high success, other concerns may arise.

[0007] More particularly, due to the relatively small thickness ofatrial tissue formed within a PV, it is likely that ablation of thistissue may in fact cause the PV to shrink or constrict. Because PV'shave a relatively small diameter, a stenosis may result. Even further,other vital bodily structures are directly adjacent each PV. Thesestructures may be undesirably damaged when ablating within a PV.

[0008] In light of the above, an alternative technique has beensuggested whereby a continuous ablation lesion pattern is formed in theleft atrium wall about the ostium associated with the PV in question. Inother words, the PV is electrically isolated from the left atrium byforming an ablation lesion pattern that surrounds the PV ostium. As aresult, any undesired electrical impulse generated within the PV couldnot propagate into the left atrium, thereby eliminating unexpected atriacontraction.

[0009] Unfortunately, while PV isolation via a continuous ablationlesion pattern about the PV ostium appears highly viable, no acceptableablation catheter configuration exists. Most atrial fibrillationablation catheters have linear distal ends, designed for manipulation ina sliding fashion along the atrial wall. That is to say, the distal,electrode-carrying end of the catheter is typically slid along (orparallel to) the atrial wall. With this generally accepted configurationin mind, it may be possible to shape the distal, electrode-carrying endinto a small ring sized in accordance with the PV ostium. For example,U.S. Pat. No. 5,617,854 discloses one such possibility. Moreparticularly, the described ablation catheter includes a substantiallyring-shaped portion sized to contact the ostium of the coronary sinus.Pursuant to conventional designs, the ring extends linearly from thecatheter body. In theory, the ring-shaped portion may be placed about aPV ostium. However, proper positioning would be extremely difficult andtime consuming. More particularly, it would be virtually impossible tolocate and then align the ring about a PV ostium when sliding thecatheter along the atrium wall. The ring must be directed toward theostium in a radial direction (relative to a central axis of the ostium).Even if the electrophysiologist were able to direct the ring to theostium, the periodic blood flow through the PV would likely force thering away from the atrium wall, as the catheter body would not provideany support.

[0010] A related concern entails mapping of a PV prior to ablation. Incases of atrial fibrillation, it is necessary to identify theorigination point of the undesired electrical impulses prior toablation. Thus, it must first be determined if the electrical impulseoriginates within one or more PVs. Once the depolarizing tissue has beenidentified, necessary ablation steps can be taken. Mapping is normallyaccomplished by placing one or more mapping electrodes into contact withthe tissue in question. In order to map tissue within a PV, therefore, arelatively straight catheter section maintaining two or more mappingelectrodes must be extended axially within the PV. Ablation cathetersconfigured to slide along the atrial wall cannot include a separate,distal extension for placement within the PV. Instead, an entirelyseparate mapping catheter must be provided and then removed forsubsequent replacement with the ablation catheter. Obviously, theseadditional steps greatly increase the overall time required to completethe procedure.

[0011] Electrical isolation of a pulmonary vein via an ablation lesionpattern surrounding the pulmonary vein ostium presents a potentiallyrevolutionary technique for treatment of atrial fibrillation. However,the unique anatomical characteristics of a pulmonary vein and leftatrium render currently available ablation catheters minimally useful.Therefore, a substantial need exists for an ablation catheter designedfor consistent positioning of one or more ablation electrodes about apulmonary vein ostium, as well as for providing pulmonary vein mappinginformation.

SUMMARY OF THE INVENTION

[0012] One aspect of the present invention provides a catheter assemblyfor treatment of cardiac arrhythmia. The catheter assembly includes acatheter body and at least one electrode. The catheter body includes aproximal portion, an intermediate portion and a distal portion. Theintermediate portion extends from the proximal portion and defines alongitudinal axis. The distal portion extends from the intermediateportion and forms a substantially closed loop transverse to thelongitudinal axis. The electrode is disposed along the loop. With thisconfiguration, upon activation, the electrode ablates a continuouslesion pattern in a plane substantially perpendicular to thelongitudinal axis. When placed about an ostium of a vessel associatedwith a chamber formed within a patient, the continuous lesion patternestablished by the electrode electrically isolates the vessel from thechamber. For example, the catheter assembly may be provided fortreatment of atrial fibrillation whereby the lesion pattern in formed toelectrically isolate a pulmonary vein (vessel) from the left atrium(chamber). In one preferred embodiment, the catheter assembly furtherincludes a mapping device for mapping tissue within the vessel.

[0013] Another aspect of the present invention relates to a catheterassembly for treatment of cardiac arrhythmia. The catheter assemblycomprises a catheter body and at least one electrode. The catheter bodyincludes a proximal portion, an intermediate portion and a distalportion. The intermediate portion extends from the proximal portion anddefines a longitudinal axis. The distal portion extends from theintermediate portion and forms a substantially closed loop. The loopdefines a loop axis substantially parallel to the longitudinal axis. Theelectrode is disposed along the loop. With this configuration, uponenergization, the electrode ablates a continuous lesion pattern in aplane substantially perpendicular to the longitudinal axis. When placedin contact with tissue, the electrode ablates a continuous lesionpattern, isolating tissue within the lesion pattern. For example, thecatheter assembly may be provided for treatment of atrial fibrillationwhereby the lesion pattern is formed to electrically isolate a pulmonaryvein from the left atrium. In one preferred embodiment, the catheterassembly further includes a mapping device extending distal the loop formapping tissue.

[0014] Another aspect of the present invention relates to a method forforming an ablation pattern to electrically isolate a vessel, definingan ostium, from a chamber formed within a patient for treatment ofcardiac arrhythmia. The method includes selecting a catheter assemblycomprising a catheter body and at least one electrode. The catheter bodydefines a longitudinal axis and includes a proximal portion and a distalportion. The distal portion forms a substantially closed loop transverseto the longitudinal axis, the loop defining a loop axis substantiallyparallel to the longitudinal axis. The electrode is disposed along theloop. The distal portion of the catheter body is guided into the chamberand is directed to a position spaced from the vessel ostium, with theloop axis being substantially aligned with a center of the vesselostium. The distal portion is advanced in a direction parallel with theloop axis such that the loop contacts the chamber wall about the vesselostium. Finally, the electrode is energized to ablate a continuouslesion pattern about the vessel ostium to electrically isolate thevessel from the chamber. For example, the method may be utilized toelectrically isolate a pulmonary vein (vessel) from the left atrium(chamber) by forming a lesion pattern about the pulmonary vein ostium.In one preferred embodiment, the method further includes mapping thevessel with a mapping electrode.

[0015] Yet another aspect of the present invention relates to a methodof electrically isolating a vessel from a chamber formed within apatient, the vessel defining an ostium in a wall of the chamber, fortreatment of cardiac arrhythmia. The method includes ablating acontinuous, closed lesion pattern in the chamber wall about the vesselostium. The lesion pattern electrically isolates the vessel from thechamber. For example, the method may be utilized to electrically isolatea pulmonary vein from the left atrium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1A is a side-elevational view of a catheter assembly inaccordance with the present invention;

[0017]FIG. 1B is a perspective view of a portion of the catheterassembly of FIG. 1A;

[0018]FIG. 1C is an end view of a portion of the catheter assembly ofFIG. 1A;

[0019]FIG. 1D is an end view of a portion of an alternative catheterassembly in accordance with the present invention;

[0020] FIGS. 2A-2D illustrates use of the catheter assembly of FIG. 1Awithin a heart;

[0021]FIG. 3A is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0022]FIG. 3B is an end view of the catheter assembly of FIG. 3A;

[0023]FIG. 3C is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0024]FIG. 3D is a simplified cross-sectional view of a portion of theheart and a portion of the catheter assembly of FIGS. 3A and 3B;

[0025]FIG. 4A is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0026]FIG. 4B illustrates placement of the catheter assembly of FIG. 4Awithin the left atrium of a heart;

[0027]FIG. 5A is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0028]FIG. 6 is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0029]FIG. 7 is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0030]FIG. 8 is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0031]FIG. 9A is a side view of a portion of an alternative catheterassembly in accordance with the present invention, in a deployedposition;

[0032]FIG. 9B is a side view of the catheter assembly of FIG. 9A in aretracted position;

[0033]FIG. 10 is a side view of a portion of an alternative catheterassembly in accordance with the present invention;

[0034]FIG. 11 is a side view of a portion of an alternative catheterassembly in accordance with the present invention; and

[0035]FIGS. 12A and 12B are side views of a portion of an alternativecatheter assembly in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] One preferred embodiment of a catheter assembly 20 in accordancewith the present invention is shown in FIGS. 1A-1C. The catheterassembly 20 is comprised of a catheter body 22, a handle 24 andelectrodes 26. As described in greater detail below, the catheter body22 extends from the handle 24, and the electrodes 26 are disposed alonga portion of the catheter body 22.

[0037] The catheter body 22 is defined by a proximal portion 28, anintermediate portion 30 and a distal portion 32, and includes a centrallumen (not shown). Although not specifically shown, the catheter bodymay be configured for over-the-wire or rapid exchange applications. Inone preferred embodiment, the proximal portion 28, the intermediate 30and the distal portion 32 are integrally formed from a biocompatiblematerial having requisite strength and flexibility for deployment withina heart. Appropriate materials are well known in the art and includepolyamide.

[0038] The intermediate portion 30 extends from the proximal portion 28.The proximal portion 28 and the intermediate portion 30 are preferablyflexible, so as to facilitate desired articulation during use. Ingeneral terms, however, the intermediate portion 30 defines alongitudinal axis L1. It should be recognized that in one position(shown in FIG. 1A), the longitudinal axis L1 extends linearly throughthe intermediate portion 30 and the proximal portion 28. Upondeployment, it may be that the proximal portion 28 and/or theintermediate portion 30 is forced to a curved or curvilinearorientation. With this in mind, the longitudinal axis L1 is morespecifically defined as a center of the intermediate portion 30 adjacenta point of intersection between the distal portion 32 and theintermediate portion 30, as best shown in FIG. 1C.

[0039] The distal portion 32 extends from the intermediate portion 30and forms a loop 34. In one preferred embodiment, the loop 34 iscircular, formed in a plane transverse to the longitudinal axis L1. Tothis end, the distal portion 32 preferably includes a lateral segment36. The lateral segment 36 extends in a generally lateral fashion fromthe intermediate portion 30. The loop 34 extends from the lateralsegment 36 in an arcuate fashion, turning or revolving about a centralloop axis C1 (shown best in FIG. 1B). While the loop 34 is shown in FIG.1A as forming a single revolution about the central loop axis C1, theloop 34 may instead include a plurality of revolutions to define aspiral or coil. In the one preferred embodiment depicted in FIGS. 1A-1C,the central loop axis C1 is aligned with the longitudinal axis L1.Alternatively, however, the lateral segment 36 may be eliminated suchthat the loop 34 extends directly from the intermediate portion 30. Evenfurther, the lateral segment 36 may be configured such that the centralloop axis C1 is offset from the longitudinal axis L1. Regardless of theexact construction, however, the central loop axis C1 is preferablysubstantially parallel to the longitudinal axis L1.

[0040] As best shown in FIG. 1C, the loop 34 preferably extends to forma circle in a frontal plane. Alternatively, a variety of other shapesmay also be useful. For example, as shown in FIG. 1D, a square-shapedloop is depicted. The loop 34 may further assume a triangular,rectangular, octagonal, or other closed shape. Returning to FIGS. 1A-1C,regardless of the exact shape, the loop 34 is preferably substantiallyclosed and can be defined by a proximal end 40 and a distal end 42. Toeffectuate the preferred “closed” configuration of the loop 34, thedistal end 42 is preferably adjacent the proximal end 40. In fact, thedistal end 42 may contact the proximal end 40, although thisrelationship is not required. Alternatively, the distal end 42 may belongitudinally spaced from the proximal end 40. With this configuration,the distal portion 32 is preferably sufficiently flexible such that uponcontact with a tissue wall, the distal end 42 will deflect proximally toa position adjacent the proximal end 40.

[0041] Regardless of the exact shape, the loop 34 preferably defines anenclosed area A greater than a size of an ostium (not shown) associatedwith a particular vessel to be isolated, as described in greater detailbelow. In one preferred embodiment, the catheter assembly 20 isconfigured to electrically isolate a pulmonary vein from the leftatrium. With this one preferred application, where the loop 34 iscircular, the loop 34 has a diameter in the range of approximately 10-20mm, more preferably 15 mm, although other sizes, either greater orsmaller, are acceptable.

[0042] The loop 34 may be formed in a variety of ways, such as byincorporating a preformed section of super elastic, shape memorymaterial, such as Nitinol, with a loop configuration. To facilitateguiding of the distal portion 32 into a heart (not shown), the catheterassembly 20 may include a stylet (not shown) internally disposed withinthe catheter body 22. In an extended position, the stylet would extendthrough the distal portion 32, so as to render the loop 34 straight.Upon retraction of the stylet, the distal portion 32 would form the loop34. Alternatively, the catheter assembly 20 may include a sheath (notshown) slidably receiving the catheter body 22. Prior to deployment, thedistal portion 32 would be retracted within the sheath, rendering theloop 34 straight. Upon deployment from the sheath, the distal portion 32would form the loop 34. Other similar approaches for providing the loop34 are similarly acceptable.

[0043] The handle 24 is preferably sized to be grasped by a user andincludes an electrical connector 44. The electrical connector provideselectrical connections to the electrodes 26 carried by the distalportion 32. To this end, wire(s) (not shown) may extend within thecentral lumen (not shown) from the distal portion 32 to the handle 24.

[0044] The electrodes 26 are preferably of a type known in the art andare preferably a series of separate band electrodes spaced along theloop 34. Instead of, or in addition to, separate band electrodes, theelectrodes 26 may include one or more spiral or coil electrodes, or oneor more counter-electrodes. Additionally, the electrodes 26 arepreferably non-thrombogenic, non-coagulum or char forming. Theelectrodes 26 may be cooled by a separate source (not shown), such as asaline source. The electrodes 26 may be electrically isolated from oneanother, or some or all of the electrodes 26 may be electricallyconnected to one another. Preferably, however, at least one electrode 26is provided. The electrodes 26 are preferably shaped and positioned suchthat during an ablation procedure, a continuous, closedtherapeutically-effective lesion pattern is created. Preferably, thelength of each of the electrodes 26 is about 4-12 mm, more preferablyabout 7 mm. The spacing between each of the electrodes 26 is preferablyabout 1-3 mm, and more preferably about 2 mm. Finally, to effectuate acontinuous, closed lesion pattern, preferably one of the electrodes 26is disposed at the proximal end 40 of the loop 34, and another of theelectrodes 26 is disposed at the distal end 42. As previously described,it is not necessary that the loop segment 38 be formed such that theproximal end 40 and the distal end 42 are integral. Instead, a slightspacing may exist. With this in mind, the spacing or gap between theelectrode 26 at the proximal 40 and the electrode 26 at the distal end42 is preferably less than about 5 mm.

[0045]FIGS. 2A and 2B illustrate use of the catheter assembly 20 shownin FIGS. 1A-1C within a heart 50. As a point of reference, the heart 50includes a right atrium RA, a left atrium LA, a right ventricle RV and aleft ventricle LV. An inferior vena cava IVC and a superior vena cavaSVC lead into the right atrium RA. The right atrium RA is separated fromthe left atrium LA by an interarterial septum (not shown). Finally, fourpulmonary veins PV extend from the left atrium LA. Each of the pulmonaryveins PV forms an ostium PVO in the left atrium LA wall. As previouslydescribed, during formation of the heart 50, it is possible that tissueof the left atrium LA may grow upwardly into one or more of thepulmonary veins PV. This left atrium LA tissue may spontaneouslydepolarize, resulting in atrial fibrillation. Notably, the heart 50 maybe formed such that a separate ostium PVO is not formed for eachindividual pulmonary vein PV. In other words, a single pulmonary veinostium PVO may be formed for two pulmonary veins PV. For example, asingle pulmonary vein ostium PVO may be formed for both the leftinferior pulmonary vein PV and the left superior pulmonary vein PV, withthe two pulmonary veins PV bifurcating from the single ostium PVO.

[0046] As shown in FIG. 2A, electrical isolation of a pulmonary vein PVbegins by directing the distal portion 32 of the catheter body 22through the inferior vena cava IVC, into the right atrium RA through apuncture in the interarterial septum (not shown) and into the leftatrium LA. Alternatively, the introduction of the distal portion 32 ofthe catheter body 22 into the right atrium RA is also suggested bypassage of the distal portion 32 into the right atrium RA through thesuperior vena cava SVC. The loop 34 is positioned slightly spaced fromthe ostium PVO associated with the pulmonary vein PV to be treated. Moreparticularly, the loop 34 is positioned such that the central loop axisC1 (FIG. 1B) is approximately aligned with a center of the pulmonaryvein ostium PVO. The catheter body 22 is then advanced distally suchthat the loop 34 contacts the left atrium LA wall about the pulmonaryvein ostium PVO in question, as shown in FIG. 2B. In other words, thecatheter body 22 is advanced in a direction parallel with the centralloop axis C1 such that the loop 34 contacts the left atrium LA wall,surrounding the pulmonary vein ostium PVO. Importantly, because thecentral loop axis C1 is parallel to the longitudinal axis L1, thecatheter body 22 longitudinally supports advancement of the loop 34. Inother words, the longitudinal axis L1 is effectively aligned with thepulmonary vein ostium PVO such that blood flow from the pulmonary veinPV acts along the longitudinal axis L1. Thus, the catheter body 22limits deflection of the loop 34 otherwise caused by blood flow from thepulmonary vein PV.

[0047] The electrodes 26 (shown best in FIGS. 1A-1C) are then energizedto a sufficient level to ablate the contacted tissue, for example withan r.f. source. In one preferred embodiment, the electrodes 26 ablatethe left atrium LA tissue for 30-120 seconds at a temperature in therange of approximately 60-70 degree C. As a result, a continuous, closedlesion pattern is formed around the pulmonary vein ostium PVO as shownin FIG. 2C. Pursuant to the above described catheter assembly 20configuration, the lesion pattern is formed in a plane substantiallyperpendicular to the longitudinal axis L1. Notably, while the lesionpattern is shown as being only slightly larger than the pulmonary veinostium PVO, the loop 34 (FIG. 1A) may be sized to produce an even largerablation lesion pattern. To this end, where a single pulmonary veinostium PVO is formed for two pulmonary veins PV, the resulting pulmonaryvein ostium PVO may be elongated. As shown in FIG. 2D, then, the loop 34(FIG. 1A) is configured to form a continuous, closed lesion patternabout the elongated-shaped pulmonary vein ostium PVO.

[0048] The continuous, closed lesion pattern electrically isolates thepulmonary vein PV from the left atrium LA. Any undesired electricalimpulses generated in the pulmonary vein are effectively “stopped” atthe lesion pattern, and will not propagate into the left atrium LA.

[0049] An alternative catheter assembly 60 is shown in FIGS. 3A and 3B.The catheter assembly 60 includes a catheter body 62, a handle (notshown) and electrodes 64. The catheter body 62 includes a proximalportion (not shown), an intermediate portion 66 and a distal portion 68.For ease of illustration, the handle and the proximal portion of thecatheter body 22 are not shown in FIGS. 3A and 3B, it being understoodthat these components are similar to the handle 24 and the proximalportion 28 shown in FIG. 1A. Similar to the catheter body 22, theintermediate portion 66 extends from the proximal portion and defines alongitudinal axis L2. The distal portion 68 extends from theintermediate portion 66 and forms a loop or coil 70 substantiallytransverse to the longitudinal axis L2 and includes a plurality of loopsegments 72A-72C. The coil 70 is formed such that each of the loopsegments 72A-72C revolves about a central loop axis C2. In one preferredembodiment, the central loop axis C2 is aligned with the longitudinalaxis L2 defined by the intermediate portion 66. Alternatively, thecentral loop axis C2 may be offset from the longitudinal axis L2.Regardless, the central loop axis C2 is preferably substantiallyparallel with the longitudinal axis L2.

[0050] Each of the loop segments 72A-72C preferably defines a differentdiameter. For example, the first loop segment 72A defines a diameterslightly larger than that of the second loop segment 72B; whereas thesecond loop segment 72B defines a diameter slightly greater than that ofthe third loop segment 72C. In this regard, while each of the loopsegments 72A-72C are depicted as being longitudinally spaced (such thatthe loop 70 forms a multi-lane spiral or coil), the loop segments72A-72C may instead be formed in a single plane (such that the loop 70forms a unitary plane spiral or coil). While the loop segments 72A-72Cextend distal the intermediate portion 66 so as to define a descendingor decreasing diameter, an opposite configuration may also be employed.For example, FIG. 3C depicts a coil 70′ having loop segments distallyincreasing in diameter.

[0051] Returning to FIGS. 3A and 3B, the electrodes 64 are similar tothe electrodes 26 (FIG. 1A) previously described, and preferably areband electrodes disposed along the loop segments 72A-72C. In thisregard, each of the loop segments 72A-72C includes electrodes 64A-64C,respectively. In one preferred embodiment, a power source (not shown)associated with the electrodes 64 is configured to individually energizethe electrodes 64 to varying levels. Further, the electrodes 64 arepreferably configured to provide feedback information indicative oftissue contact, such as by including a thermocouple.

[0052] The catheter assembly 60 is used in a fashion highly similar tothe method previously described for the catheter assembly 20 (as shown,for example, in FIGS. 2A-2C). Thus, for example, the distal portion 68of the catheter body 62 is directed within the left atrium LA (FIG. 2A)such that the loop 70 is disposed about a pulmonary vein ostium PVO. Itshould be understood that one or more of the loop segments 72A-72C maydefine a diameter (or area) that is less than a diameter (or area) ofthe pulmonary vein ostium PVO in question. For example, in thesimplified cross-sectional view of FIG. 3D, the electrodes 64Cassociated with the third loop segment 72C (FIG. 3A) are not in contactwith the left atrium LA wall, but instead are within the area defined bythe pulmonary vein ostium PVO. Conversely, the electrodes 64B associatedwith the second loop segment 72B (FIG. 3A) and the electrodes 64Aassociated with the first loop segment (FIG. 3A) are in contact with theleft atrium LA wall. To avoid potential collateral damage caused by fullenergization of the electrodes 64C not in contact with the left atriumLA wall, each of the electrodes 64A-64C are selectively energized with alow energy supply. The energy level is not sufficient to ablatecontacted tissue, but provides a low energy measurement, such as througha thermocouple or other sensing device associated with each of theelectrodes 64A-64C. If the sensing device detects a temperature rise, anindication is given that the particular energized electrode 64A, 64B or64C is in contact with tissue of the left atrium LA. Following the lowenergy measurement procedure, only those electrodes determined to be incontact with the left atrium LA (for example, electrodes 64A and 64B)are powered to ablate a continuous, closed lesion pattern about thepulmonary vein ostium PVO, as previously described.

[0053] Another alternative embodiment of a catheter assembly 80 is shownin FIG. 4A. The catheter assembly 80 includes a catheter body 82, anelectrode 84 and a locating device 86. For ease of illustration, only aportion of the catheter assembly 80 is shown, and catheter assembly 80may further include a handle similar to the handle 24 associated withthe catheter assembly 20 (FIG. 1A) previously described.

[0054] Catheter body 82 is defined by a proximal portion (not shown), anintermediate portion 88 and a distal portion 90. The intermediateportion 88 extends from the proximal portion and is defined by aproximal segment 92 and a distal segment 94. In a preferred embodiment,the distal segment 94 is preferably more flexible than the proximalsegment 92. With this configuration, the distal segment 94 can moreeasily deflect relative to the proximal segment 92, thereby facilitatingdesired positioning of the distal portion 90 during deployment. In thisregard, an internal pull wire (not shown) may be provided to effectuatedesired deflection of the distal segment 94. Even further, an anchor 96is preferably included for facilitating a more radical displacement ofthe distal portion 90 relative to the intermediate portion 88.

[0055] As with previous embodiments, the intermediate portion 88 definesa longitudinal axis L3. Once again, where the intermediate portion 88 isaxially aligned with the proximal portion (not shown), the longitudinalaxis L3 is linear along the intermediate portion 88 and the proximalportion. However, because the intermediate portion 88 is preferablybendable relative to the proximal portion, and further because thedistal segment 94 may bend relative to the proximal segment 92, thelongitudinal axis L3 is more succinctly defined by the intermediateportion 88 at the point of intersection between the intermediate portion88 and the distal portion 90.

[0056] Similar to the catheter assembly 20 (FIG. 1A) previouslydescribed, the distal portion 90 preferably forms a loop 98. The loop 98may include one or more loop segments (one is shown in FIG. 4A), witheach loop segment revolving around a central loop axis C3. The loop 98is formed substantially transverse to the longitudinal axis L3, with thecentral loop axis C3 preferably aligned with the longitudinal axis L3.Alternatively, the central loop axis C3 may be slightly offset from thelongitudinal axis L3. Regardless, the central loop axis C3 is preferablyparallel with the longitudinal axis L3.

[0057] The electrode 84 is shown in FIG. 4 as being a continuous coilelectrode. Alternatively, a plurality of spaced, band electrodes orcounter-electrodes may be used.

[0058] Finally, the locating device 86 includes a tip 100 configured toextend distal the loop 98. In one preferred embodiment, the locatingdevice 86 is integrally formed with the catheter body 82, extending fromthe distal portion 90. Alternatively, the locating device 86 may be aseparate body. Regardless, the tip 100 extends distal the distal portion90, and is aligned with the central loop axis C3 defined by the loop 98.The tip 100 preferably has a diameter less than a diameter of apulmonary vein, and a length in the range of approximately 1-15 mm.Further, as shown in FIG. 4, the tip 100 may include a series of mappingelectrodes 102. The mapping electrodes 102 are electrically connected toan external recording system (not shown) for providing informationindicative of tissue polarization.

[0059] As shown in FIG. 4B, during use, the catheter assembly 80 isdirected into the left atrium LA as previously described. The locatingdevice 86, and in particular the tip 100, is then used to locate thepulmonary vein ostium PVO. Once located, the tip 100 is inserted intothe pulmonary vein PV, effectively centering the loop 98 around thepulmonary vein ostium PVO. Where the tip 100 includes the mappingelectrodes 102, a mapping procedure can be performed, wherebyinformation indicative of tissue activity nearby the mapping electrodes102 is provided. During this mapping procedure, a determination can bemade as to whether the particular pulmonary vein PV is generatingundesired electrical impulses. Where it is determined that, in fact,tissue in the pulmonary vein PV is spontaneously depolarizing, theelectrode 84 is energized to form the continuous, closed lesion patternabout the pulmonary vein ostium PVO as previously described.

[0060] Yet another alternative embodiment of a catheter assembly 110 inaccordance with the present invention is shown in FIG. 5. The catheterassembly 110 is highly similar to the catheter assembly 80 (FIG. 4A) andincludes a catheter body 112, electrodes 114 and a locating device 116.The catheter body 112 includes a proximal portion (not shown) anintermediate portion 88 defining a longitudinal axis L4 and a distalportion 120. The distal portion 120 extends from the intermediateportion 118 and forms a loop 122 substantially transverse to thelongitudinal axis L4. In this regard, the loop 122 revolves about acentral loop axis C4. In one preferred embodiment, the central loop axisC4 is aligned with the longitudinal axis L4. Alternatively, the centralloop axis C4 is offset from, but substantially parallel with, thelongitudinal axis L4. The electrodes 114 (shown as spaced bandelectrodes) are disposed along the loop 122 for forming a continues,closed lesion pattern.

[0061] The locating device 116 includes a tip 124 that extends distalthe loop 122. In one preferred embodiment, the locating device 116 isintegrally formed with the catheter body 112 and includes mappingelectrodes 126 connected to an external recording device (not shown).Alternatively, the locating device 116 may be a separate body. As shownin FIG. 5, the tip 124 forms a descending diameter coil, generallyaligned with the central loop axis C4. By providing a coil configurationfor the tip 124, the tip 124 facilitates a more positive centering ofthe loop 122 about a pulmonary vein ostium PVO (FIG. 4B). In onepreferred embodiment, the tip 124 defines a maximum diameterapproximating a diameter of a pulmonary vein. When inserted within apulmonary vein, then, the tip 124 effectively lodges along the pulmonaryvein wall. This, in turn, positions the loop 122 in a more centralfashion about the associated ostium. Further, by providing the mappingelectrodes 126, the locating device 116 additionally serves as a mappingdevice for evaluating a particular pulmonary vein.

[0062] It should be recognized that other devices can be provided toassist in centering the ablation loop about the pulmonary vein ostium.For example, yet another alternative embodiment of a catheter assembly130 is depicted in FIG. 6. The catheter assembly includes a catheterbody 132, electrodes 134, a balloon 136 and a locating device 138. Thecatheter body 132 is similar to those previously described, and includesa proximal portion (not shown) an intermediate portion 140 defining alongitudinal axis L5 and a distal portion 142. The distal portion 142extends from the intermediate portion 140 and forms a loop 144substantially transverse to the longitudinal axis L5. The loop 144revolves about a central loop axis C5, that, in one preferredembodiment, is aligned with the longitudinal axis L5. The balloon 136 isdisposed along the distal portion 142 distal the loop 144. In onepreferred embodiment, the balloon 136 is fluidly connected to a fluidsource (not shown), such as a pressurized reservoir of saline, by alumen (not shown) formed within the catheter body 132. Finally, thelocating device 138 includes a tip 146 extending distal the loop 144. Inone preferred embodiment, as shown in FIG. 6, the locating device 138 isintegrally formed with the catheter body 132, with the tip 146 extendingdistal the balloon 136. Alternatively, the locating device 138 may be aseparate body, and the tip 146 may be positioned between the loop 144and the balloon 136. Regardless, the tip 146 preferably includes mappingelectrodes 148.

[0063] During use, the locating device 138 is used to locate a pulmonaryvein PV (FIG. 4B) via the tip 146. The tip 146 axially inserted into thepulmonary vein PV. The mapping electrodes 148 may then be used toascertain whether tissue in the pulmonary vein PV is spontaneouslygenerating unexpected electrical impulses. Upon determining that thepulmonary vein PV requires electrical isolation, the catheter body 132is deployed such that the loop 144 contacts the left atrium LA (FIG. 4B)wall (as previously described). The balloon 136 is inflated such that itengages the pulmonary vein PV wall. Once inflated, the balloon 136positively centers the loop 144 about the pulmonary vein ostium PVO(FIG. 4B).

[0064] Yet another alternative embodiment of a catheter assembly 160 isshown in FIG. 7. The catheter assembly 160 includes a catheter body 162,electrodes 164, a wire basket 166 and a locating device 168. As withprevious embodiments, the catheter body 162 includes a proximal portion(not shown), an intermediate portion 170 defining a longitudinal axis L6and a distal portion 172. The distal portion 172 extends from theintermediate portion 170 and forms a loop 174 transverse to thelongitudinal axis L6. In this regard, the loop 174 revolves around acentral loop axis C6 that, in one preferred embodiment, is aligned withthe longitudinal axis L6.

[0065] The wire basket 166 is maintained by the distal portion 172distal the loop 174. The wire basket 166 may be radially extended andretracted via a pull wire or similar activation device extending througha lumen (not shown) formed within the catheter body 162.

[0066] Finally, the locating device 168 includes a tip 176 positioneddistal the loop 174. In one preferred embodiment, the locating device168 is integrally formed with the catheter body 162 and includes mappingelectrodes 178. Alternatively, the locating device 168 may be a separatebody, and the tip 176 may be disposed between the wire basket 166 andthe loop 174.

[0067] During use, the catheter assembly 160 functions in a fashionhighly similar to the catheter assembly 130 (FIG. 6) previouslydescribed. The locating device 168, and in particular the tip 176, isused to locate and map a pulmonary vein PV (FIG. 4B). The loop 174 ismaneuvered into contact with the left atrium LA (FIG. 4B) wall. The wirebasket 166 is then radially deployed so as to engage the pulmonary veinPV wall. In this deployed position, the wire basket 166 serves topositively center the loop 174 about the pulmonary vein ostium PVO (FIG.4B).

[0068] Yet another alternative embodiment of a catheter assembly 190 isshown in FIG. 8. The catheter assembly 190 includes a catheter body 192(shown partially in FIG. 8), electrodes 194, a locating device 196 and aguide catheter or sheath 198. As described in greater detail below, thesheath 198 coaxially maintains the catheter body 192 and the locatingdevice 196 such that each of the catheter body 192 and the locatingdevice 196 are slidable between a retracted position and a deployedposition (shown in FIG. 8).

[0069] The catheter body 192 is virtually identical to the catheter body62 (FIG. 3A) previously described and includes a proximal portion (notshown), an intermediate portion 200 defining a longitudinal axis L7 anda distal portion 202. The distal portion 202 extends from theintermediate portion 200 and forms a coil or plurality of loops 204substantially transverse to the longitudinal axis L7. Alternatively, thecoil 204 may form a single loop. The coil 204 revolves around a centralloop axis C7, that, in one preferred embodiment, is aligned with thelongitudinal axis L7. The distal portion 202, and in particular the coil204, is preferably sufficiently flexible so as to assume a relativelystraight configuration when retracted within the sheath 198. Further,the distal portion 202 includes a shape memory characteristic such thatwhen deployed from the sheath 198, the distal portion 202 forms the coil204 as shown in FIG. 8.

[0070] The electrodes 194 are identical to those previously describedand preferably comprise band electrodes disposed along the coil 204.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

[0071] The locating device 196 is relatively rigid and includes a shaft206 defining a tip 208 that preferably maintains mapping electrodes 210.The shaft 206 is sized to be slidably received within a lumen (notshown) in the sheath 198. As shown in FIG. 8, the tip 208 preferablyassumes a coil shape with decreasing diameter. Alternatively, the tip208 may be substantially straight. Preferably, however, the tip 208 issufficiently flexible such that upon retraction into the sheath 198, thetip 208 assumes a relatively straight form. Additionally, the tip 208has a shape memory characteristic such that upon deployment from thesheath 198, the tip 208 assumes the coiled shape shown in FIG. 8. Forexample, the tip 208 may include stainless steel or Nitinol core wires.Further, the tip 208 may be formed from a shape memory alloy of Nitinolthat forms the coil shape when heated above a certain temperature. Theheat may be achieved through resistive heating of the wire directly, orby surrounding the wire with a tubular heater.

[0072] The sheath 198 includes a proximal end (not shown) and a distalend 212, and forms at least one central lumen (not shown) sized tomaintain the catheter body 192 and the locating device 196.Alternatively, a separate lumen may be provided for each of the catheterbody 192 and the locating device 196. Regardless, the sheath 198 isconfigured to slidably maintain each of the catheter body 192 and thelocating device 196 in a relatively close relationship. In one preferredembodiment, the sheath 198 is formed of a relatively soft material suchas 35D or 40D Pebex.

[0073] As described above, each of the catheter body 192 and thelocating device 196 are slidable relative to the sheath 198. In adeployed position (depicted in FIG. 8), the distal portion 202 of thecatheter body 192 and the tip 208 of the locating device 196 extenddistally from the sheath 198. More particularly, the locating device 196is positioned such that the tip 208 is distal the coil 204. In thisextended position, the tip 208 is essentially aligned with the centralloop axis L7.

[0074] During use, the catheter body 192 and the locating device 196 areretracted within the sheath 198. The sheath 198 is then guided to theleft atrium LA (FIG. 4B). The catheter body 192 and the locating device196 are deployed from the sheath 198. More particularly, the distalportion 202 of the catheter body 192 and the tip 208 of the locatingdevice 196 are extended from the distal end 212 of the sheath 198 (asshown in FIG. 8). A locking device (not shown) is preferably provided tosecure the catheter assembly 190 in the deployed position. As previouslydescribed, upon deployment, the distal portion 202 forms the coil 204,whereas the tip 208 preferably assumes a coil shape. The tip 208 locatesand is directed axially into a pulmonary vein PV as previouslydescribed. The mapping electrodes 210 sample electrical activity of thepulmonary vein tissue. If the mapping procedure determines that thepulmonary vein PV requires electrical isolation, the sheath 198 isguided in a direction along the central loop axis C7 until the coil 204contacts the left atrium LA (FIG. 4B) wall about the pulmonary veinostium PVO (FIG. 4B). Because the catheter body 192 and the locatingdevice 196 are directly connected by the sheath 198, the tip 208effectively positively centers the loop 204 about the pulmonary veinostium PVO. The electrodes 194 may be selectively energized with a lowenergy supply to determine which of the electrodes 194 are in contactwith tissue of the left atrium LA. Some or all of the electrodes 194 arethen energized to ablate a continuous, closed lesion pattern about thepulmonary vein ostium PVO, thereby electrically isolating the pulmonaryvein PV from the left atrium LA.

[0075] While the catheter assembly 190 has been described as includingthe sheath 198 to maintain the catheter body 192 and the locating device196, the sheath 198 may be eliminated for example, the catheter body 192may alternatively be configured to include lumen (not shown) sized toslidably receive the locating device 192. In this regard, the locatingdevice 192 may serve as a guide wire, with the catheter body 192 ridingover the locating device 192 much like an over-the-wire catheterconfiguration commonly known in the art. Even further, the catheter body192 may include a rapid exchange design characteristic for quickmounting to removal from the locating device 190.

[0076] Yet another alternative embodiment of a catheter assembly 220 isshown in FIGS. 9A and 9B. The catheter assembly 220 includes a catheterbody 222 (shown partially in FIGS. 9A and 9B), electrodes 224, stylets226 and a locating device 228. The electrodes 224 are disposed along aportion of the catheter body 222. The stylets 226 are slidablymaintained within the catheter body 222. Finally, the locating device228 is slidably maintained by the catheter body 222.

[0077] The catheter body 222 is similar to those previously describedand includes a proximal portion (not shown), an intermediate portion230, defining a longitudinal axis L8, and a distal portion 232. Thedistal portion 232 forms a loop 234 substantially transverse to thelongitudinal axis L8. The loop 234 revolves around a central loop axisC8 which, in one preferred embodiment, is aligned with the longitudinalaxis L8. The distal portion 232 is preferably sufficiently flexible soas to be relatively straight in a retracted position (FIG. 9B). Further,the distal portion 232 has a shape memory characteristic such that thedistal portion 232 forms the loop 234 in a deployed position (FIG. 9A).For example, the catheter body 222 may be formed of a super elastic,shape memory Nitinol alloy.

[0078] Each of the stylets 226 are relatively rigid shafts sized to beslidably received within lumens (not shown) formed by the catheter body222. To this end, as shown in FIG. 9A, in a deployed position, thestylets 226 are proximal the distal portion 232 such that the distalportion 232 is allowed to form the loop 234. Conversely, in a retractedposition (FIG. 9B) the stylets 226 extend into the distal portion 232,thereby rendering the distal portion 232 substantially straight.

[0079] The electrodes 224 are identical to those previously describedand preferably comprise band electrodes disposed along the loop 234.Alternatively, a continuous coil electrode or counter electrode may beprovided.

[0080] The locating device 228 includes a shaft 236 having a tip 238.Similar to previous embodiments, the tip 238 is preferably coil shaped,and includes mapping electrodes 240. In this regard, the tip 238 ispreferably sufficiently flexible such that in the retracted position(FIG. 9B), the tip 238 is rendered relatively straight by the catheterbody 222. Conversely, in the deployed position (FIG. 9A), the tip 238assumes the coiled shape. Alternatively, the tip 238 may besubstantially straight in the deployed position.

[0081] The catheter assembly 220 is used in a manner highly similar tothat previously described. The catheter assembly 220 is initially placedin the retracted position (FIG. 9B), whereby the stylets 226 aremaneuvered distally to straighten the distal portion 232. Further, thelocating device 228 is retracted within the catheter body 222 such thattip 238 is proximal the distal portion 232 and is rendered relativelystraight. In this retracted position, the catheter assembly 222 can moreeasily be directed into the left atrium LA (FIG. 4B) as previouslydescribed. Once in the left atrium LA, the catheter assembly 220 ismaneuvered to the deployed position (FIG. 9A), whereby the stylets aremoved proximally such that the distal portion 232 forms the loop 234.Further, the locating device 228 is maneuvered distally relative to thecatheter body 222 such that the tip 238 extends distal the loop 234. Inthe deployed position, the locating device 228 is maneuvered in agenerally axial fashion to locate and extend into a pulmonary vein PV.The mapping electrodes 240 map the pulmonary vein tissue (FIG. 4B).Where the mapping procedure indicates that the pulmonary vein PVrequires electrical isolation, the catheter assembly 220 is advancedsuch that the loop 234 surrounds the pulmonary vein ostium PVO (FIG.4B). More particularly, the catheter assembly 220 is advanced in thedirection of the central loop axis C8. Once again, the uniqueconfiguration of the catheter assembly 220 facilitates movement in anaxial direction (relative to the pulmonary vein ostium PVO) as opposedto a radial, sliding direction required by previous ablation catheterdesigns. Notably, because the locating device 228 is directly connectedto the catheter body 222, the locating device 228 facilitates positivecentering of the loop 234 about the pulmonary vein ostium PVO. Theelectrodes 224 are then energized to ablate a continuous, closed lesionpattern about the pulmonary vein ostium PVO, thereby electricallyisolating the pulmonary vein PV.

[0082] Yet another alternative embodiment of the catheter assembly 250in accordance with the present invention is shown in FIG. 10. Thecatheter assembly 250 includes a catheter body 252 (shown partially inFIG. 10), electrodes 254, a locating device 256 and a guide catheter orsheath 258. As described in greater detail below, the sheath 258coaxially maintains the catheter body 252 and the locating device 256such that each of the catheter body 252 and the locating device 256 areslidable between a retracted position and a deployed position (shown inFIG. 10).

[0083] The catheter body 252 is virtually identical to the catheter body62 (FIG. 3A) previously described and includes a proximal portion (notshown), an intermediate portion 260 defining a longitudinal axis L9 anda distal portion 262. The distal portion 262 extends from theintermediate portion 260 and forms a coil or loops 264 substantiallytransverse to the longitudinal axis L9. Alternatively, the coil 264 mayform a single loop. The coil 264 revolves around a central loop axis C9,that, in one preferred embodiment, is aligned with the longitudinal axisL9. The distal portion 262, and in particular the coil 264, ispreferably sufficiently flexible so as to assume a relatively straightconfiguration when retracted within the sheath 258. Further, the distalportion 262 includes a shape memory characteristic such that whendeployed from the sheath 258, the distal portion 262 forms the coil 264as shown in FIG. 10.

[0084] The electrodes 254 are identical to those previously describedand preferably comprise band electrodes disposed along the coil 264.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

[0085] The locating device 256 includes a shaft 266 and a balloon 268.The shaft 266 includes a distal portion 270 and a tip 272. The distalportion 270 preferably forms an expansion joint 274. The tip 272 isdistal the expansion joint 274 and preferably maintains mappingelectrodes 276. The balloon 268 is sealed to the distal portion 270 ofthe shaft 266 about the expansion joint 274. In this regard, theexpansion joint 274 is configured to be manipulated between a contractedposition (FIG. 10) and an expanded position. In the expanded position,the expansion joint 274 extends axially so as to collapse the balloon268. When collapsed, the balloon 268 can more easily be retracted withinthe sheath 258.

[0086] The sheath 258 includes a proximal end (not shown) and a distalend 278, and forms at least one central lumen (not shown) sized tomaintain the catheter body 252 and the locating device 256.Alternatively, a separate lumen may be provided for each of the catheterbody 252 and the locating device 256. Regardless, the sheath 258 isconfigured to slidably maintain each of the catheter body 252 and thelocating device 256 in relatively close relationship. In one preferredembodiment, the sheath 258 is formed of a relatively soft material suchas 35D or 40D Pebex.

[0087] As described above, each of the catheter body 252 and thelocating device 256 are slidable relative to the sheath 258. In adeployed position (depicted in FIG. 10), the distal portion 262 of thecatheter body 252 and the distal portion 270 of the locating device 256extend distally from the sheath 258. More particularly, the coil 264 ispositioned distal the distal end 278 of the sheath 258. Further, thedistal portion 270, including the balloon 268, of the locating device256 is positioned distal the coil 264. In this position, the distalportion 270 is essentially aligned with the central loop axis L9.

[0088] Prior to use, the catheter body 252 and the locating device 256are retracted within the sheath 258. The sheath 258 is then guided tothe left atrium LA (FIG. 4B). The catheter body 252 and the locatingdevice 256 are deployed from the sheath 258. More particularly, thedistal portion 262 of the catheter body 252 and the distal portion 270of the locating device 256 are extended from the distal end 278 of thesheath 258 (as shown in FIG. 10). A locking device (not shown) ispreferably provided to secure the catheter assembly 250 in the deployedposition. As previously described, upon deployment, the distal portion262 of the catheter body 252 forms the coil 264. The distal portion 270of the locating device 256, including the balloon 268, is positioneddistal the coil 264. The tip 272 locates and is directed axially into apulmonary vein PV (FIG. 4B) as previously described. The mappingelectrodes 276 sample electrical activity of the pulmonary vein tissue.If the mapping procedure determines that the pulmonary vein PV requireselectrical isolation, the sheath 258 is guided in a direction along thecentral loop axis C9 until the coil 264 contacts the left atrium LA wallabout the pulmonary vein ostium PVO (FIG. 4B). The expansion joint 274is contracted and the balloon 268 inflated. Once inflated, the balloon268 engages the pulmonary vein PV. Because the catheter body 252 and thelocating device 256 are directly connected by the sheath 258, theballoon 268 effectively positively centers the coil 264 about thepulmonary vein ostium PVO. The electrodes 254 may be selectivelyenergized with a low-energy supply to determine which of the electrodes254 are in contact with the tissue of the left atrium LA. Some or all ofthe electrodes 254 are then energized to ablate a continuous, closedlesion pattern about the pulmonary vein ostium PVO, thereby electricallyisolating the pulmonary vein PV from the left atrium LA.

[0089] Yet another alternative embodiment of a catheter assembly 290 isshown in FIG. 11. The catheter assembly 290 is highly similar to thecatheter assembly 250 (FIG. 10) previously described, and includes acatheter body 292, electrodes 294, a locating device 296 and a guidecatheter or sheath 298. The sheath 298 coaxially maintains the catheterbody 292 and the locating device 296 such that each of the catheter body292 and the locating device 296 are slidable between a retractedposition and a deployed position (shown in FIG. 11).

[0090] The catheter body 292 includes a proximal portion (not shown), anintermediate portion 300 defining a longitudinal axis L10 and a distalportion 302. The distal portion 302 extends from the intermediateportion 300 and forms a coil or plurality of loops 304 substantiallytransverse to the longitudinal axis L10. Alternatively, the coil 304 mayform a single loop. The coil 304 revolves around a central loop axisC10, that, in one preferred embodiment, is aligned with the longitudinalaxis L10. The distal portion 302, and in particular the coil 304, ispreferably sufficiently flexible so as to assume a relatively straightconfiguration when retracted within the sheath 298. Further, the distalportion 302 includes a shape memory characteristic such that whendeployed from the sheath 298, the distal portion 302 forms the coil 304as shown in FIG. 11.

[0091] The electrodes 294 are identical to those previously describedand preferably comprise band electrodes disposed along the coil 304.Alternatively, a continuous coil electrode or counter-electrode may beprovided.

[0092] The locating device 296 includes a shaft 306 and a wire basket308. The shaft 306 includes a distal portion 310 and a tip 312. Thedistal portion 310 forms an expansion joint 314. The tip 312 preferablymaintains mapping electrodes 316. The wire basket 308 is secured to thedistal portion 310 about the expansion joint 314. With thisconfiguration, the expansion joint 314 can be manipulated between anexpanded position in which the wire basket 308 is relatively flat and acontracted position (FIG. 11) in which the wire basket 308 expandsradially.

[0093] The sheath 298 is highly similar to previous embodiments andincludes a proximal end (not shown) and a distal end 318, and forms atleast one central lumen (not shown) sized to maintain the catheter body292 and the locating device 296. Alternatively, a separate lumen may beprovided for each of the catheter body 292 and the locating device 296.Regardless, the sheath 298 is configured to slidably maintain each ofthe catheter body 292 and the locating device 296 in a relatively closerelationship.

[0094] As described above, each of the catheter body 292 and thelocating device 296 are slidable relative to the sheath 298. In adeployed position (depicted in FIG. 11), the distal portion 302 of thecatheter body 292 and the distal portion 310 of the locating device 296extend distally from the sheath 298. More particularly, the catheterbody 292 is positioned such that the coil 304 is distal the distal end318. Further, the distal portion 310 of the locating device 296 isdistal the coil 304.

[0095] During use, the catheter assembly 290 functions in a mannerhighly similar to the catheter assembly 250 (FIG. 10) previouslydescribed. However, the wire basket 308 is used to positively center thecoil 304 about a pulmonary vein ostium PVO instead of the balloon 268(FIG. 10) previously described.

[0096] Yet another alternative embodiment of the catheter assembly 330is shown in FIGS. 12A and 12B. The catheter assembly 330 includes acatheter body 332 (shown partially in FIGS. 12A and 12B), a wire basket334, a locating device 336 and a stylet or guide wire 338. The wirebasket 334 is secured to the catheter body 332. The locating device 336is preferably integrally formed with the catheter body 332 and includesa balloon 340. Finally, the guide wire 338 is slidably disposed within acentral lumen (not shown) in the catheter body 332 and the locatingdevice 336.

[0097] The catheter body 332 includes a proximal portion (not shown), anintermediate 342 defining a longitudinal axis L11 and a distal portion344. The distal portion 344 maintains a proximal collar 346 and a distalcollar 348. In a preferred embodiment, the proximal collar 346 isslidable relative to the distal collar 348.

[0098] The wire basket 334 is secured to the distal portion 344 by theproximal collar 346 and the distal collar 348. Further, the wire basket334 includes a plurality of individual wire struts 350 each maintainingan electrode 352. In a preferred embodiment, the wire struts 350 arepreferably tubular and are fluidly connected to a cooling source. Theelectrodes 352 are preferably disposed along the wire struts 350,respectively, slightly distal of a central position. With thisconfiguration, the wire basket 334 can be maneuvered between a retractedposition (FIG. 12A) and an expanded position (FIG. 12B) with movement ofthe proximal collar 346 relative to the distal collar 348. Notably, inthe expanded position of FIG. 12B, the wire basket 334 positions theelectrodes 352 so as to form a loop transverse to the longitudinal axisL11. More particularly, the loop formed in the expanded positionrevolves around a central loop axis C11, that, in one preferredembodiment, is aligned with the longitudinal axis L11.

[0099] The electrodes 352 are identical to those previously describedand preferably comprise band electrodes disposed along the wire basket334.

[0100] The locating device 336 extends distal the distal collar 348, andmaintains the balloon 340 and mapping electrodes 354. The balloon 340 isfluidly connected to an inflation source (not shown) by a lumen (notshown) formed within the catheter body 332. As shown in FIGS. 12A and12B, the balloon 340 is preferably positioned distal the wire basket334. Further, the mapping electrode 354 is positioned distal the balloon340.

[0101] Prior to use, the catheter assembly 330 is positioned in theretracted position shown in FIG. 12A. The guide wire 338 is guided tothe left atrium LA (FIG. 4B) and into a pulmonary vein PV (FIG. 4B). Thecatheter body 332, including the locating device 336, are guided overthe guide wire 338 to a point adjacent the pulmonary vein. The catheterbody 332 is then advanced such that the locating device 336 enters thepulmonary vein PV. The mapping electrodes 354 sample electrical activityof the pulmonary vein tissue. If the mapping procedure determines thatthe pulmonary vein PV requires electrical isolation, the catheterassembly 330 is maneuvered to the expanded position shown in FIG. 12B,whereby the wire basket 334 expands radially. The catheter body 332 isthen advanced axially toward the pulmonary vein such that the wirebasket 334 contacts the left atrium LA about the pulmonary vein ostiumPVO (FIG. 4B). The balloon 340 is then inflated so as to engage thepulmonary vein PV. Once inflated, the balloon 340 effectively centersthe wire basket 334, and thus the electrodes 352, about the pulmonaryvein ostium PVO. The electrodes 352 are then energized to ablate acontinuous, closed lesion pattern about the pulmonary vein ostium PVO,thereby electrically isolating the pulmonary vein PV from the leftatrium LA. If necessary, the individual wire struts 350 are cooled, suchas by forcing a cooling liquid through the wire struts 350. The balloon340 is deflated and the wire basket 334 maneuvered to the contractedposition (FIG. 12A). The entire catheter assembly 330 may then beremoved from the patient. Alternatively, the catheter body 332 may beretracted from the patient along the guide wire 338 and replaced with aseparate catheter device (not shown). To this end, the catheter body 332may be configured to provide a rapid exchange feature, as would beapparent to one of ordinary skill.

[0102] The pulmonary vein isolation catheter of the present invention,and in particular the substantially closed loop configuration, providesa highly viable tool for electrically isolating a vessel, such as apulmonary vein, from a chamber, such as the left atrium. In this regard,the substantially closed loop is orientated transverse to a longitudinalaxis of the catheter assembly so as to facilitate rapid, consistentplacement of the ablation loop at a desired location along the leftatrium or other chamber wall. This transverse orientation allows forguiding of the catheter assembly in a direction parallel to the axisdefined by the vessel ostium, as opposed to a radial approach. Thus, thenumerous complications presented by prior art sliding techniques areavoided. Further, due to this transverse orientation, the catheterassembly can further be provided with a locating device extending distalthe ablation loop for easily locating a particular vessel, as well as tocenter the loop around the vessel ostium. Finally, the locating devicecan be provided with mapping electrodes such that mapping of thepulmonary vein in conjunction with ablation about the pulmonary veinostium can be achieved with a unitary device.

[0103] Although the present invention has been described with referenceto preferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, the preferred embodiment hasdescribed electrical isolation of a pulmonary vein from the left atriumfor treatment of atrial fibrillation. Alternatively, the method andapparatus of the present invention may be utilized in the treatment ofother cardiac arrhythmias, such as isolating the coronary sinus from theleft atrium or isolating the outflow tract (or pulmonary valve) from theright ventricle. Further, a number of the described embodiments haveincluded a catheter body forming a single loop. Alternatively, amulti-plane coil or spiral may be formed. The coil or spiral mayincrease or decrease in diameter as it extends distally, or may have auniform diameter. Additionally, while the loop has been described aspreferably being circular, a variety of other substantially closedshapes, including square, triangular, octagonal, etc. are equallyacceptable. Also, several of the described embodiments have included alocating device for centering the loop about a pulmonary vein ostium andfor mapping a pulmonary vein. In this regard, the locating device may beconfigured to serve only as a centering device or only as a mappingdevice, or both. Finally, other features may be incorporated into thecatheter assembly. For example, to expedite deployment, the catheterassembly may be configured to slidably receive a guide wire used toposition the catheter assembly within the left atrium. Even further, thecatheter assembly may include a rapid exchange feature for quickplacement over and removal from the guide wire.

What is claimed:
 1. A catheter assembly for treatment of cardiacarrhythmia comprising: a catheter body including: a proximal portion, anintermediate portion extending from the proximal portion and defining alongitudinal axis, a distal portion extending from the intermediateportion and forming a substantially closed loop transverse to thelongitudinal axis; and at least one electrode disposed along the distalportion; wherein upon activation, the at least one electrode ablates acontinuous, closed lesion pattern in a plane substantially perpendicularto the longitudinal axis for isolating material within the closed lesionpattern.
 2. The catheter assembly of claim 1, wherein the loop issubstantially circular.
 3. The catheter assembly of claim 1, wherein theloop is sized such that the continuous lesion pattern has a diametergreater than a diameter of a pulmonary vein ostium formed in a leftatrium.
 4. The catheter assembly of claim 1, wherein the distal portionincludes a loop segment of at least one revolution for forming the loop.5. The catheter assembly of claim 4, wherein the distal portion furtherincludes a lateral segment extending laterally from the intermediateportion, the loop section extending from the lateral section.
 6. Thecatheter assembly of claim 4, wherein the loop segment revolves about acentral loop axis substantially parallel with the longitudinal axis. 7.The catheter assembly of claim 4, wherein the loop segment includes aproximal section and a distal section, and further wherein the proximalsection is sufficiently flexible such that upon contact between thedistal section and a tissue wall, the proximal section deflects towardthe distal section with further distal movement of the catheter body. 8.The catheter assembly of claim 1, wherein the distal portion forms aplurality of loops combining to form a cylinder.
 9. The catheterassembly of claim 1, wherein the distal portion forms a plurality ofloops combining to form a cone.
 10. The catheter assembly of claim 9,wherein the plurality of loops includes a first loop segment having adiameter greater than a diameter of a pulmonary vein ostium formed in aleft atrium.
 11. The catheter assembly of claim 10, wherein theplurality of loops includes a second loop segment having a diameter lessthan a diameter of a pulmonary vein ostium formed in a left atrium. 12.The catheter assembly of claim 1, further comprising: a locating devicefor centering the loop about an ostium.
 13. The catheter assembly ofclaim 12, wherein the locating device includes a tip extending distalthe loop, the tip being sized for placement within a vessel.
 14. Thecatheter assembly of claim 13, wherein the tip forms a coil, at least aportion of the coil defining a diameter approximating a diameter of apulmonary vein.
 15. The catheter assembly of claim 13, wherein thelocating device further includes an balloon positioned distal the loop.16. The catheter assembly of claim 13, wherein the centering devicefurther includes an expandable wire basket positioned distal the loop.17. The catheter assembly of claim 12, wherein the locating device isintegrally formed with the catheter body.
 18. The catheter assembly ofclaim 12, wherein the locating device includes an elongated shaftproximal the tip, the catheter assembly further comprising: means forslidably maintaining the elongated shaft relative to the catheter body.19. The catheter assembly of claim 18, wherein the means for slidablymaintaining the shaft is a sheath coaxially receiving the shaft and thecatheter body.
 20. The catheter assembly of claim 1, further comprising:a mapping device for mapping tissue distal the loop.
 21. The catheterassembly of claim 20, wherein the mapping device includes a probe tipmaintaining at least one mapping electrode, the probe tip extendingdistal the loop.
 22. The catheter assembly of claim 21, wherein theprobe tip has a diameter less than a diameter of a pulmonary vein. 23.The catheter assembly of claim 21, wherein the probe tip forms a conicalcoil.
 24. The catheter assembly of claim 20, wherein the mapping deviceis integrally formed with the catheter body.
 25. The catheter assemblyof claim 19, wherein the mapping device includes an elongated shafthaving a probe tip at a distal end thereof, the catheter assemblyfurther comprising: means for slidably maintaining the elongated shaftrelative to the catheter body.
 26. The catheter assembly of claim 25,wherein the means for slidably maintaining the shaft is a sheathcoaxially receiving the shaft and the catheter body.
 27. The catheterassembly of claim 1, wherein the intermediate portion includes aproximal section and a distal section adjacent the distal portion, thedistal section configured to be more flexible than the proximal sectionfor allowing deflection of the distal portion relative to the proximalsection.
 28. The catheter assembly of claim 1, further comprising: anelongated guide body having a central lumen and defining a proximal endand a distal end, the catheter body being slidably maintained within thecentral lumen such that in a deployed position, the distal portion ofthe catheter body extends distally from the distal end of the guidebody, and in a retracted position, the distal portion is proximal thedistal end; wherein the distal portion is substantially straight in theretracted position.
 29. The catheter assembly of claim 28, wherein thedistal portion is made of a shape memory material such that the distalportion forms the loop in the deployed position.
 30. The catheterassembly of claim 1, wherein the catheter body includes a central lumenextending from the proximal portion to the distal portion, the catheterassembly further comprising: a stylet slidably maintained within thecentral lumen for selectively rendering the distal portion substantiallystraight.
 31. The catheter assembly of claim 1, wherein the distalportion includes a basket maintaining a plurality of electrodes, thebasket being selectively expandable to position the electrodes in a loopconfiguration transverse to the longitudinal axis.
 32. A catheterassembly for treatment of cardiac arrhythmia comprising: a catheter bodyincluding: a proximal portion, an intermediate portion extending fromthe proximal portion and defining a longitudinal axis, a distal portionextending from the intermediate portion and forming a substantiallyclosed loop, the loop defining a central loop axis substantiallyparallel to the longitudinal axis; and at least one electrode disposedalong the distal portion; wherein upon energization, the electrodeablates a continuous, closed lesion pattern in a plane substantiallyperpendicular to the longitudinal axis for isolating material within theclosed lesion pattern.
 33. The catheter assembly of claim 32, whereinthe loop is substantially circular.
 34. The catheter assembly of claim32, wherein the loop is sized such that the continuous lesion patternhas a diameter greater than a diameter of a pulmonary vein ostium formedin a left atrium.
 35. The catheter assembly of claim 32, wherein thedistal portion includes a loop segment of at least one revolution forforming the loop.
 36. The catheter assembly of claim 32, furthercomprising: a locating device for centering the loop about an ostium.37. The catheter assembly of claim 36, wherein the locating deviceincludes a tip extending distal the loop, the tip being sized forplacement within a pulmonary vein.
 38. The catheter assembly of claim32, further comprising: a mapping device for mapping tissue distal theloop.
 39. A method for forming an ablation pattern to electricallyisolate a vessel having an ostium from a chamber formed within a patientfor treatment of cardiac arrhythmia, the method including: selecting acatheter assembly comprising a catheter body defining a longitudinalaxis and having a proximal portion and a distal portion, the distalportion forming a substantially closed loop transverse to thelongitudinal axis, the loop defining a loop axis substantially parallelto the longitudinal axis, and at least one electrode disposed along thedistal portion; guiding the distal portion into the chamber; directingthe distal portion to a position spaced from the vessel ostium, wherebythe loop axis is substantially aligned with a center of the vesselostium; advancing the distal portion in a direction parallel with theloop axis such that the loop contacts the chamber wall about the vesselostium; and energizing the electrode to ablate a continuous, closedlesion pattern about the vessel ostium to electrically isolate thevessel from the chamber.
 40. The method of claim 39, wherein thecatheter assembly further includes a tip extending distal the loop, themethod further including: locating the vessel with the tip.
 41. Themethod of claim 40, wherein the tip includes a centering device, themethod further including: centering the loop about the vessel ostium viathe centering device.
 42. The method of claim 40, wherein the tipincludes at least one mapping electrode, the method further including:mapping tissue of the vessel with the mapping electrode.
 43. The methodof claim 39, wherein the distal portion includes a spiral sectiondefining a plurality of loops of varying diameter, each of the pluralityof loops maintaining at least one electrode, the method furthercomprising: selectively providing a low-level power supply to each ofthe electrodes; and determining which of the plurality of loops is incontact with the vessel wall based upon the low-level power supply. 44.The method of claim 39, wherein selecting a catheter assembly includes:selecting a catheter assembly having the catheter body and the tipintegrally formed.
 45. The method of claim 39, wherein the tip is formedon an elongated shaft, and further wherein selecting a catheter assemblyincludes selecting a catheter assembly having a sheath co-axiallymaintaining the catheter body and the elongated shaft.
 46. The method ofclaim 39, wherein the chamber is a left atrium and the vessel is apulmonary vein.
 47. A method of electrically isolating a vessel from achamber formed within a patient, the vessel defining an ostium in a wallof the chamber, for treatment of cardiac arrhythmia, the methodcomprising: ablating a continuous, closed lesion pattern in the chamberwall about the vessel ostium, the lesion pattern electrically isolatingthe vessel from the chamber.
 48. The method of claim 47, wherein thevessel is a pulmonary vein, and further wherein the lesion patterndefines an internal area at least slightly larger than an area of thepulmonary vein ostium.
 49. The method of claim 47, wherein a catheterassembly comprising a catheter body having a distal portion forming aclosed loop maintaining a plurality of electrodes is provided, andwherein ablating a continuous, closed lesion pattern includes:substantially simultaneously energizing the plurality of electrodes. 50.The method of claim 47, wherein the continuous, closed lesion pattern isformed with a single catheter assembly.
 51. The method of claim 50,wherein the catheter assembly includes a catheter body defining alongitudinal axis and having a proximal portion and a distal portion,the distal portion forming a substantially closed loop transverse to thelongitudinal axis, the loop defining a loop axis and maintaining atleast one electrode, the method further including: positioning the loopabout the vessel ostium prior to ablating the continuous, closed lesionpattern.
 52. The method of claim 51, wherein positioning the loopincludes: directing the distal portion into the chamber such that theloop axis is substantially aligned with a center of the vessel ostium;and advancing the distal portion in a direction substantially parallelwith the loop axis such that the loop contracts the chamber wall aboutthe vessel ostium.
 53. The method of claim 51, wherein the loopmaintains a plurality of electrodes, the method further including:determining which of the plurality of electrodes are in contact withchamber wall before ablating the continuous, closed lesion pattern. 54.The method of claim 50, wherein the catheter assembly further includes amapping probe, the method further including: mapping the vessel with themapping probe before ablating the continuous, closed lesion pattern.